Sewage discharge (aka black water) is nasty stuff. When I had a sewer line backup in a home I was renting, the (very cheap) landlord spent a bunch on mitigation. Carpets replaced fully, sheetrock cut 12+ inches up and replaced, wood treated with nasty chemicals that killed any potential bad things, redid the kitchen cabinets (came out of the dishwasher). I'm not a professional so I won't give advice on your particular situation, but don't cheap out on your family's health.